Trans fatty acids: EFSA Panel reviews dietary intakes and health effects
The Scientific Panel on Dietetic Products, Nutrition and Allergies (NDA) of the European Food Safety Authority (EFSA) published today an opinion relating to the presence of trans fatty acids (TFAs) in foods and the effect on human health of the consumption of trans fatty acids. Trans fatty acids, like saturated fatty acids, raise LDL (or “bad”) cholesterol levels in the blood, thereby increasing the risk of coronary heart disease (CHD). The panel concluded that at equivalent dietary levels, the effect of trans fatty acids on heart health may be greater than that of saturated fatty acids. However, current intakes of trans fatty acids are generally more than 10-fold lower than those of saturated fatty acids whose intakes in many European countries exceed dietary recommendations. The NDA panel also evaluated other health effects and concluded that scientific evidence with regards to a possible relationship of TFA intake with cancer, type 2 diabetes or allergies is weak or inconsistent. Finally, the panel advised that there are no analytical methods available to distinguish between TFAs from natural sources and those formed during food processing.
In carrying out its risk assessment on trans fatty acids, EFSA’s NDA panel reviewed evidence concerning both TFAs naturally present in foods, such as in certain animal fats (e.g. dairy, beef, lamb and mutton fat), and those occurring as a result of manufacturing processes, for instance hydrogenation of oils (e.g. certain margarines and fat spreads).
The Panel found that the intake of trans fatty acids varies between countries, with lowest intakes found in the Mediterranean countries. The contribution of TFAs to daily energy intake (based on estimates for 1995/1996) is approximately 0.5-2.0% in comparison with that of saturated fats which ranges from 10.5 to 18%. Recent dietary surveys indicate that TFA intakes have decreased in a number of EU countries, mainly due to the reformulation of food products (e.g. fat spreads) to reduce the TFA content.
Evidence from many human studies indicates that --as for saturated fatty acids-- increasing dietary intake of trans fatty acids (when compared to cis-monounsaturated or cis-polyunsaturated fatty acids) raises blood levels of LDL cholesterol (Low Density Lipoprotein – considered as ‘bad’ cholesterol), thereby increasing the risk of coronary heart disease (CHD). The rise in LDL cholesterol is proportional to the amount of TFAs consumed. These studies also show that for equivalent dietary levels, TFAs may increase the risk of coronary heart disease more than saturates. This is because – unlike saturates – TFAs also reduce blood levels of HDL cholesterol (High Density Lipoprotein – considered as ‘good’ cholesterol) and increase blood levels of triglycerides. However, average intakes of TFAs in European diets are generally more than 10-fold lower than those of saturates.
Commenting on these conclusions, Professor Albert Flynn, Chair of EFSA’s NDA Panel stated: “Evidence from human intervention trials, strengthened by findings from epidemiological studies, supports the idea that the effect of trans fatty acids on heart health may be greater than that of saturated fats. However, given current intake levels of TFAs, their potential to significantly increase cardiovascular risk is much lower than that of saturates which are currently consumed in excess of dietary recommendations in many European countries.”
Concerning other health implications, human studies revealed no consistent evidence of any effect of TFAs on blood pressure or on other markers associated with risk of CHD (for instance, platelet aggregation), or on insulin sensitivity associated with diabetes. Epidemiological evidence for a possible relationship of TFA intake with cancer, type 2 diabetes, or allergy is weak or inconsistent. No causal link has been established for the suggested adverse effects of TFAs on foetal and infant development.
In most of the intervention studies, monounsaturated TFAs from hydrogenated vegetable oils were evaluated. It is not possible to determine whether there are differences in the health effects of TFAs according to the source (ie TFAs from ruminant fat in comparison with those found in hydrogenated vegetable oils). In addition, there is no method of analysis applicable to a wide range of foods which can distinguish between TFAs which are naturally present in foods (e.g. dairy and beef fat) and those formed during the processing of hydrogenated oils.
The risk assessment conducted by the EFSA NDA Panel is based on a question raised by the European Commission. In March 2003 the Danish Authorities adopted legislation which introduced limits on the level of trans fatty acids in oils and processed foodstuffs containing fats and oils as ingredients, with the exception of naturally occurring trans fatty acids in animal fat. According to the Danish Authorities the measure was justified on public health grounds in order to minimise the risk of cardiovascular disease. As the views of Member states differed, the European Commission decided to ask EFSA for a scientific opinion on the occurrence of trans fatty acids in the diet and its implications for human health.
Fatty acids can be classified according to their number of double bonds. Saturated fatty acids have no double bonds, while monounsaturated fatty acids have one double bond and polyunsaturated fatty acids have two or more double bonds. Trans fatty acids are unsaturated fatty acids that have at least one double bond in the trans configuration. Most unsaturated fatty acids in food have a cis structure but the trans configuration also occurs in foods.
Trans fatty acids are principally formed when liquid oils are made into solid fats like shortening and hard margarine. Hydrogenation – or the process of adding hydrogen to vegetable oil -- increases the shelf life and flavor stability of foods containing these fats. Trans fatty acids are also formed during heating and frying of oils at high temperatures. In addition, TFAs are found naturally, principally in animal-based foods (eg dairy and beef fat) as a result of bacterial transformation of unsaturated fatty acids in the rumen (first stomach) of ruminant animals.
Dairy and beef fat typically contains around 3-6% TFAs (% of total fatty acids) while levels in lamb and mutton can be somewhat higher. TFA levels in most edible fats are below 1-2%. Vegetable oils and liquid margarines have a low proportion of TFAs, usually below 1%. The TFA content of bakery products (rusks, crackers, biscuits etc…) as well as some breakfast cereals with added fat, French fries, soup powders and some sweet and snack products may vary considerably (from below 1% up to 30%) depending on the type of fat used.
In the EU, mean daily intakes of TFAs for 14 different countries were estimated to range from 0.5-2.1% and 0.8-1.9% of total energy intakes among men and women, respectively (Transfair study, 1995-96). Intakes of TFAs were lowest in the Mediterranean countries. Mean intakes of saturated fatty acids ranged from 10.5 to 18% of total energy intake, with the lowest intakes in Southern Europe. Health authorities have recommended that the contribution of saturated fatty acids to total energy intakes should not exceed 10% in order to reduce the risk of coronary heart disease.